package com.example.animation;

import android.support.v4.view.ViewPager;
import android.view.View;


public class DepthPageTransformer implements ViewPager.PageTransformer
{
	private static final float MIN_SCALE = 0.75F;


	@Override
	public void transformPage(View view, float position)
	{
		int pageWidth = view.getWidth();

		if(position < -1)
		{
			// [-Infinity,-1)
			// this page is way off-screen to the left
			view.setAlpha(0);
		}
		else if(position <= 0)
		{
			// [-1,0]
			// use the default slide transition when moving to the left page
			view.setAlpha(1);
			view.setTranslationX(0);
			view.setScaleX(1);
			view.setScaleY(1);
		}
		else if(position <= 1)
		{
			// (0,1]
			// fade the page out
			view.setAlpha(1 - position);

			// counteract the default slide transition
			view.setTranslationX(pageWidth * -position);

			// scale the page down (between MIN_SCALE and 1)
			float scaleFactor = MIN_SCALE + (1 - MIN_SCALE) * (1 - Math.abs(position));
			view.setScaleX(scaleFactor);
			view.setScaleY(scaleFactor);
		}
		else
		{
			// (1,+Infinity]
			// this page is way off-screen to the right
			view.setAlpha(0);
		}
	}
}
